1. Field of the Invention
The present invention relates to, for example, a seam welding apparatus for cutting a trailing end of a leading plate and a leading end of a trailing plate and bonding them together in a process line of metal plates, and more particularly to a seam welding apparatus including a movable portion of a leading plate clamp means adapted to be tiltable for holding the leading plate for overlap alignment, a movable portion of a trailing plate clamp means adapted to be movable toward the leading plate while holding the trailing plate, a shearing, means adapted for cutting the trailing end of the leading plate held by the movable portion of the leading plate clamp means and the leading end of the trailing plate held by the movable portion of the trailing plate clamp means before the overlap alignment, a trailing plate clamp moving means adapted to move the movable portion of the trailing plate clamp means for overlapping and aligning the leading end of the sheared trailing plate with the trailing end of the leading plate toward the leading plate, and a welding machine adapted to weld the overlapped alignment portion of the trailing end and the leading end in a transverse direction of the plates, and a seam welding method.
2. Related Art
FIGS. 17, 18 and 19 show a conventional seam welding apparatus used in a process line of metal plates, which is substantially the same as that shown in Japanese Patent Application Laid-Open No. 5-212549. FIG. 17 is a schematic frontal view of FIG. 1 of that publication for the sake of simplification, FIG. 18 is a left side elevational view and FIG. 19 is a cross-sectional view taken along the line Axe2x80x94A of FIG. 18.
Also, FIGS. 20 to 23 are views showing the steps of the conventional seam welding apparatus shown in FIGS. 17 to 19. FIG. 24 is a plan view of the conventional apparatus. FIG. 25 is a side elevational view showing the overlap condition. FIG. 26 is an enlarged perspective view showing the overlap portion. FIG. 27 is a perspective view showing a carriage C frame.
In FIGS. 17 to 27, for example, in the case where a thickness of the final welded overlapped alignment portion of the two components (plates) to be welded may exceed 130% of a thickness of the original single plate or alternatively in the case where the restrictive weld quality is not needed, the amount of the overlapped alignment portion of the two plates is increased; that is, the width of the overlapped alignment portion is increased so that a width from a start of weld to an end of weld, i.e., the overlapped alignment amount may be kept constant.
However, in contrast, for example, in the case where the thickness of the final welded overlapped alignment portion must be very small like the case where the thickness is not to exceed the range of 105% to 130% of the original single plate, or alternatively in the case where a very high standard is to be applied to the enhancement of the joint quality including the weld strength, if the width of the overlapped alignment portion from the start of weld to the end of weld is kept constant, in order to maintain the amount (width) at a certain level upon welding, it is necessary to impart the function for fixing the components to be welded firmly thereto. However, it is more effective and general to give the function for compensating the overlapped alignment amount thereto.
For instance, in advance, in view of an escape amount of the overlapped and aligned plates generated gradually from the start end side of weld to the end side of weld assuming that the most suitable overlapped alignment amount at the weld start end be represented by L1 in accordance with various parameters such as material, thickness, hardness or the like of the leading plate 1 and the trailing plate 2, the overlapped alignment amount at the end of weld is compensated for to the overlapped alignment amount L2 that is larger than the overlapped alignment amount L1 at the end of weld by the escape amount. It is less expensive to impart such a compensation function to the apparatus than to provide a strong fixing means in manufacturing the seam welding apparatus.
Working steps in the conventional seam welding apparatus provided with such a compensation function will now be described with reference to FIGS. 17 to 27.
Old First Step
First of all, in FIG. 20, the trailing end of the leading plate 1 and the leading end of the trailing plate 2 are kept stopped at a suitable cutting distance in a cutting position within the seal welding apparatus.
Old Second Step
Subsequently, in FIG. 21, a moving portion 3a of a leading plate clamp means for holding the leading plate 1 and a movable portion 4a of a trailing plate clamp means for holding the trailing plate 2 are moved to predetermined positions, and the leading plate 1 and the trailing plate 2 are firmly clamped by the two clamps, respectively.
Old Third Step
Subsequently, in FIG. 22, the shearing means is provided integrally with a trailing end cutter for cutting the trailing end of the leading plate and a leading end cutter for cutting the leading end of the trailing plate that are engaged with each other from above and from below, respectively. In this example, a double cut shear provided in the carriage C frame 5 serves as this. A lower blade unit 6 of the double cut shear having a U-shaped cross-section is raised and at the same time, an upper blade unit 7 having a U-shaped cross-section is lowered to thereby simultaneously cut the trailing end of the leading plate 1 and the leading end of the trailing plate 2 in parallel.
Old Fourth Step
Subsequently, in FIG. 23, after the completion of the shearing action by the above-described shearing means, the lower blade unit 6 is lowered and at the same time, the upper blade unit 7 is raised to bring the double cut shear back to the original position.
Old Fifth Step
In this example, subsequently, in order to overlap and align the trailing end of the leading plate 1 and the leading end of the trailing plate 2 with each other, the movable portion 3a of the leading plate clamp means is tilted so that the trailing end of the leading plate 1 is located over the other.
Old Sixth Step
Subsequently, during the operation from the above-described old first step to the old fifth step, i.e., to the original position, in order to overlap and align, an advance end stop position for stopping when the movable portion 4a of the trailing plate clamp means is advanced toward the movable portion 3a of the leading plate clamp means is adjusted in advance.
This will be described with reference to FIG. 19 and FIGS. 24 to 26.
In FIGS. 24, 25 and 26, first of all, in order to obtain the optimum overlapped alignment amount L1 at the weld start end, an interval between a weld start end adjusting stopper 9 mounted on the moving portion 4a of the trailing plate clamp means for moving toward the moving portion 3a of the leading plate clamp means, and a weld start end adjusting stopper 11 mounted on a fixed portion 4b of the trailing plate clamp means for moving by a weld start end overlapped alignment amount adjusting and driving unit 10 is adjusted to a distance obtained by adding L11 in view of the mounting width position W2 of the weld start end adjusting stopper 9 and the weld start end adjusting stopper 11 to the cutting width L0 with respect to the plate width W1 of the plates to be welded.
On the other hand, in order to obtain the optimum overlapped alignment amount L2 at the weld terminal end, an interval between a weld terminal end adjusting stopper 12 mounted on the moving portion 3a of the leading plate clamp means for moving toward the movable portion 3a of the leading plate clamp means and a weld terminal end adjusting stopper 14 mounted on a fixed portion 4b of the trailing clamp means for moving by a weld terminal end overlapped alignment amount adjusting and driving unit 13 is adjusted to a distance obtained by adding L21 in view of the mounting width position W2 of the weld terminal end adjusting stopper 12 and the weld terminal end adjusting stopper 14 to the cutting width L0 with respect to the plate width W1 of the plates to be welded.
Old Seventh Step
After the positions of the weld start end adjusting stopper 11 and the weld terminal end adjusting stopper 14 have been thus adjusted, the movable portion 4a of the trailing plate clamp means is moved toward the moving portion 3a of the leading plate clamp means by clamp forwarding cylinders 15a and 15b mounted on the fixed portion 4b of the trailing plate clamp means. Thereafter, if the tilt of the tilted movable portion 3a of the leading plate clamp means in the foregoing fifth step is returned back, the overlap and alignment that is needed for welding may be performed as shown in FIGS. 25 and 26.
Old Eighth Step
Subsequently, in FIG. 27, an upper electrode unit 17 mounted on an upper electrode pressurizing unit 16 is lowered by the lowering pressurizing operation of the upper electrode pressurizing unit 16.
Also, an upper electrode wheel 18 mounted rotatably on the upper electrode unit 17 and a lower electrode wheel 20 mounted rotatably on a lower electrode unit 19 are brought into contact with each other while subjected to the weld pressure.
Old Ninth Step
Subsequently, in FIGS. 17, 18 and 19, the carriage C frame 5 is moved by a carriage C frame moving unit 24 while a weld current is caused to flow from a weld power source unit 21 through an upper conductive member 22, the upper electrode unit 17, the upper electrode wheel 18, the lower electrode wheel 20, the lower electrode unit 19 and a lower conductive member 23 (FIG. 18).
Thus, the upper electrode wheel 18 and the lower electrode wheel 20 are caused to ride over the overlapped alignment portion of the leading plate 1 and the trailing plate 2 while moving the carriage C frame 5, thereby welding in the transverse direction of the plates.
In the above-described conventional steps, in order to maintain the stop position firmly when the movable portion 4a of the trailing plate clamp means moves toward the movable portion 3a of the leading plate clamp means, it is necessary to provide a strong enough force to resist so as not to reduce the overlapped alignment amount by the component of the weld pressure upon welding.
FIG. 28 is a cross-sectional view showing a state before the melting by the welding the overlapped alignment portion, and FIG. 30 is a cross-sectional view showing a state immediately before the welded condition.
In the metal plates as the members to be welded, for example, if the thickness t is 3 mm and the tension "sgr" is 60 kgf/mm2, the weld pressure F is 3,000 kgf and the overlapped alignment amount xcex41 at the weld start end is the same as the plate thickness at 3 mm. These parameters are determined generally experimentally.
FIG. 29 is a view showing the weldpressure immediately before the melting and its component. A slip angle xcex81 has a horizontal portion of the weld overlap portion. However, since the weld current until the melting is caused to flow therethrough, a plastic deformation easily occurs in the members to be welded. In this example, the slip angle is 26.6 degrees. Also, if 2xcex81 is a wedge angle, the component P1 by the weld pressure at this time becomes 2,995 kgf (1=F X cos xcex8{fraction (1/2)}xc3x97sin xcex81).
In FIG. 30, in a condition infinitely close to the completion of the welding, the molten surface angle xcex82 is 45 degrees and the component P2 due to the weld pressure is 1,500 kgf. Furthermore, a component to exclude the molten material corresponding to a hatched area in FIG. 30 is applied.
This component is close to the infinite value until the overlapped alignment amount becomes zero unless the leading plate 1 and the trailing plate 2 have elastic deformation in the traveling direction of the metal strips, i.e., the leading plate 1 and the trailing plate 2. However, in reality, since the elastic deformation occurs on the welding machine side in addition to the members to be welded or the slippage gap of the guides exists or the like, the force becomes about 1.5 to 2 times of the above-described component P.
This component is supported mainly by the trailing plate clamp forwarding cylinder 15a at the weld start end side, and is supported mainly by the trailing plate clamp forwarding cylinder 15b at the weld terminal end side.
As described above, in order to resist the large components by the weld pressure, conventionally, a high output is obtained by using cylinders actuated at, for example, a high hydraulic pressure exceeding 7.0 Mpa in general as the trailing plate clamp forwarding cylinders 15a and 15b. 
However, if such a high hydraulic pressure is used to provide a large output, it is necessary to arrange a high pressure resistive pipe to cause a problem that the piping cost or maintenance cost is increased in comparison with a low pressure resistive pipe.
Also, there is a problem that an oil leakage would be likely to occur.
On the other hand, in order to solve such a problem, if cylinders that operate at a low pressure, for example, 1.0 Mpa or less are used simply instead of the conventional cylinders that operate at a high hydraulic pressure, a diameter of the cylinders for obtaining the predetermined high output has to be extremely increased. As a matter of fact, it is difficult to arrange the apparatus. This does not solve the problem actually.
An object of the present invention is to provide a seam welding apparatus and a seam welding method that may overcome the above-described defects, and operates at a low pressure to obtain a suitable overlapped alignment amount.
In a first aspect of this invention, a seam welding apparatus including a movable portion of a leading plate clamp means adapted to be tiltable for holding the leading plate for overlap alignment, a movable portion of a trailing plate clamp means adapted to be movable toward the leading plate while holding the trailing plate, a shearing means adapted for cutting the trailing end of the leading plate held by the movable portion of the leading plate clamp means and the leading end of the trailing plate held by the movable portion of the trailing plate clamp means before the overlap alignment, a trailing plate clamp moving means adapted to move the movable portion of the trailing plate clamp means for overlapping and aligning the leading end of the sheared trailing plate with the trailing end of the leading plate toward the leading plate, and a welding machine adapted to weld the overlapped alignment portion of the trailing end and the leading end in a transverse direction of the plates,
is characterized in that the trailing plate clamp moving means comprises a link mechanism for overlapping and aligning the leading end of the trailing plate with the trailing end of the leading plate in a fully extended condition or in the vicinity of the fully extended condition and a link drive source for actuating the link mechanism. Note that, hereinbelow, xe2x80x9ca fully extended condition or in the vicinity of the fully extended conditionxe2x80x9d is referred to simply as xe2x80x9ca fully extended conditionxe2x80x9d.
In a second aspect of this invention, a seam welding apparatus according to claim 1, is characterized in that the trailing plate clamp moving means includes a pair of link mechanism along both side edges of the trailing plate.
In a third aspect of this invention, a seam welding apparatus according to claim 2, is characterized in that the pair of link mechanisms are coupled with a link drive source to form a parallel link mechanism assembled through a coupling link for simultaneously actuating the pair of link mechanism.
In a fourth aspect of this invention, a seam welding apparatus according to any one of claims 1 to 3, is characterized in that the movable portion of the leading plate clamp means has tilt pivots arranged, respectively, on the weld start end side and the weld terminal end side in a transverse direction of the leading plate, either one of the tilt pivots of the weld start end side and the weld terminal end side is arranged to be movable so that the overlapped alignment amount may be adjusted and moved by an overlapped alignment adjusting link mechanism provided with an overlapped alignment adjusting and driving source.
In a fifth aspect of this invention, a seam welding apparatus according to claim 4, is characterized in that the overlapped alignment amount adjusting link mechanism is arranged to be identified with the overlapped alignment direction in the fully extended condition, and the overlapped alignment adjusting and driving source is coupled substantially in a direction perpendicular to the overlapped alignment direction.
In a sixth aspect of this invention, a seam welding apparatus according to claim 3, is characterized in that the other end, which is not coupled with the movable portion of the trailing plate clamp means, of the link mechanism of the weld start end side and the weld terminal end side forming the trailing plate clamp moving means is supported movably so that the overlapped alignment amount may be adjusted.
In a seventh aspect of this invention, a seam welding apparatus according to claim 6, is characterized in that the other end, which is not coupled with the movable portion of the trailing plate clamp means, of the link mechanism of the weld start end side and the weld terminal end side forming the trailing plate clamp moving means is adjusted and moved by a receiving portion for bearing such other end, a guide portion for guiding the receiving portion movably, and an overlapped alignment amount adjusting and driving source for moving the guide portion.
In an eighth aspect of this invention, a seam welding apparatus according to claim 3, characterized in that the other end, which is not coupled with the movable portion of the trailing plate clamp means, of the link mechanism of the weld start end side and the weld terminal end side forming the trailing plate clamp moving means is moved in the transverse direction of the trailing plate.
In a ninth aspect of this invention, a seam welding apparatus according to any one of claims 1 to 3, characterized in that the shearing means is provided with a trailing end cutter for cutting the trailing end of the leading plate and a leading end cutter for cutting the leading end of the trailing plate and a cutting interval between the trailing end cutter and the leading end cutter is adapted so that the overlapped alignment amount at the weld terminal end side is greater than the overlapped alignment amount of the weld start end side in advance when the plates are to be overlapped with each other.
In a tenth aspect of this invention, a seam welding method using the seam welding apparatus according to any one of claims 1 to 3, characterized in that the plates are cut by the shearing means in advance when the plates are to be overlapped and aligned with each other so that the overlapped alignment amount at the weld terminal end side is greater than the overlapped alignment amount at the weld start end side, and the pair of link mechanisms forming the trailing plate clamp moving means are extended through an equal distance to thereby obtain a desired overlapped alignment amount.
In an eleventh aspect of this invention, a seam welding apparatus according to any one of claims 1 to 3, characterized in that the movable portion of the leading plate clamp means has tilt pivots arranged, respectively, to the weld start end side and the weld terminal end side in the transverse direction of the leading plate, a shaft of the tilt pivot on the weld start end side is used as an eccentric shaft, a shaft of the tilt pivot on the weld terminal end side is an eccentric shaft having a larger eccentric amount than that of the aforesaid eccentric shaft on the weld start end side, and the overlapped alignment amount, relative to the trailing plate, of the leading plate held by the movable portion of the leading plate clamp means is adjustable by the eccentric shaft drive source for rotating both the eccentric shafts individually.
In a twelfth aspect of this invention, a seam welding apparatus according to claim 11, characterized in that the shearing means is provided with a trailing end cutter for cutting the trailing end of the leading plate and a leading end cutter for cutting the leading end of the trailing plate, and a cutting interval between the trailing end cutter and the leading end cutter is adapted so that the overlapped alignment amount at the weld terminal end side is greater than the overlapped alignment amount of the weld start end side in advance when the plates are to be overlapped with each other.